1. Field of the Invention
The present invention relates to antiperspirant compositions in the form of solid sticks. The compositions herein comprise three phases, one of which is an antiperspirant phase containing antiperspirant materials, a second of which is an alcohol gel phase which can contain deodorant materials and a third of which is a barrier phase isolating and insulating the other two phases from each other.
2. The Prior Art
Antiperspirant compositions in stick form are known in the art. Single phase antiperspirant compositions have, for example, been disclosed in Taub; U.S. Pat. No. 1,984,669; issued Dec. 18, 1934 and Procter & Gamble; British Pat. No. 1,433,695; granted Aug. 25, 1976. Stick compositions of this type typically employ large amounts of waxy materials as the vehicle which delivers the antiperspirant active to the skin. The antiperspirant active materials often are present in the stick in particulate form which is particularly effective. Such stick products are stable and are especially effective for delivering large amounts of antiperspirant salts to the skin.
Attempts have been made to realize deodorant and antiperspirant sticks which deliver active ingredients to the skin via a vehicle which glides easily over the skin surface and which imparts a cooling sensation to the skin both during and after application. Soap/alcohol gels can provide such cosmetic benefits. However, incorporation of conventional astringent antiperspirant salts into such gels tends to interfere with the gel structure and render it less cosmetically desirable. To solve such compatibility problems, soap/alcohol gel sticks have been formulated using special additives such as lactate salts. (See, for example, Teller; U.S. Pat. No. 2,732,327, issued Jan. 24, 1956 and Slater; U.S. Pat. No. 2,900,306, issued Aug. 18, 1959). Some soap/alcohol gel antiperspirant sticks have also been formulated in two phases with an inner core containing gel-compatible antiperspirant salts and an outer shell containing deodorant materials (See Bell, U.S. Pat. No. 2,970,083, issued Jan. 31, 1961).
Combinations of a conventional waxy antiperspirant composition with a soap/alcohol gel to form a two-phase stick composition could enhance composition efficacy and improve composition cosmetic benefits. Such combination is, however, not made without certain difficulties. While each phase alone of such a stick composition is stable, contact between the two phases can cause destructive interaction between the two phases. The alcohol/gel phase experiences syneresis which is a bleeding or leaking of the gelled alcohol from the gel structure or matrix. Such leaked alcohol can interact with components of the waxy phase and can thus consume or physically separate the phases, thereby resulting in an unacceptable consumer product.
It is speculated herein that this problem of interfacial interaction is due to, or at least exacerbated by, the presence of particulate materials in the antiperspirant phase. Often, the particulate material present in the antiperspirant phase is the antiperspirant active material itself. The particulate may be present, however, merely as a filler or inert component. The ability of the barrier phase to affect gel pH is also a factor in product stability.
Given the state of the antiperspirant art as described above, there is a continuing need for new and useful antiperspirant stick compositions which are stable and which provide both good antiperspirant efficacy as well as desirable application characteristics. Accordingly, it is an object of the present invention to provide multi-phase antiperspirant sticks with effective antiperspirancy performance and desirable application characteristics.
It is a further object of the present invention to provide multi-phase antiperspirant sticks which are dimensionally stable.
It is a further object of the present invention to provide such multi-phase antiperspirant sticks which do not exhibit severe interfacial interaction.
It is a further object of the present invention to provide multi-phase antiperspirant sticks which can deliver both antiperspirant and deodorant materials to the skin simultaneously.
It has been surprisingly discovered that the above objectives can be realized and superior multi-phase antiperspirant sticks provided by formulating a stick having a thin waxy barrier of specific composition and which is relatively free of particulate materials and has an appropriate pH. This third barrier phase prevents interfacial interaction when present in the region interjacent to a solid shearable antiperspirant phase which preferably utilizes particular amounts of certain types of waxes, emollients and particulate antiperspirant actives and a gel phase formulated with particular amounts of certain polyhydric alcohols and gel-forming agents.